Spine doesn't do vector graphics at all, sorry. It does only raster graphics. This is mainly because rendering SVG or other vector graphics in games and other applications is difficult and takes more processing power than raster graphics. That's the same reason most games use raster graphics. Many other tools support SVG because they only need to render inside their editor
they don't provide runtimes for many programming languages and game toolkits like Spine does and they don't need to consider rendering performance in all those environments.
However, you can do something similar using meshes. For example, you can use a small image that is entirely white and create a mesh for it. You can then bind it to bones so you can bend it around, and you can tint it any color. You could build up a whole character using this technique and it would render accurately at different resolutions. There's a single color example here, where the growing rose is done that way:
(but don't watch the video any farther, cringe! :p)